Conditioning the air within an enclosure has been accomplished by a self-contained unit employing a refrigeration cycle with the unit generally located within an opening in the enclosure. In order to both heat and cool the air within the enclosure, the reversible type of refrigeration apparatus has been used containing two heat exchangers, one located within the enclosure and the other outside the enclosure exposed to the outdoor air. These heat exchangers operate interchangeably as a condenser and an evaporator to both heat and cool the enclosure. Control means are provided by which reversal of the operating cycle can be obtained. The apparatus provided with a sump located beneath the outside coil. Troughs in the base pan conduct condensate dropping from the inside coil to this sump. Condensate removal means are provided for directing the condensate onto the condenser, cooling it and disposing of the condensate by evaporation. Condensate from the outdoor coil collects in this sump when the outdoor heat exchanger is operating as an evaporator on the heating cycle; accordingly, none of this water is disposed of by evaporation and builds up as it is splashed over the outdoor coil by the condensate removal means. The apparatus may also at times have to operate on the heating cycle when a below-freezing outside temperature has frozen this sump water, locking the fan rigid. This usually results in blown fuses or damaged parts when the apparatus is operated.
Some prior art attempts have provided drains in the condensate sump such as disclosed in U.S. Pat. No. 2,777,303-Slattery, assigned to the General Electric Company, the assignee of the present invention. The patent teaches the use of a thermally responsive element that cooperatively opens the sump drain when the outside temperature falls below a predetermined temperature to drain the sump of any condensate that may have collected. U.S. Pat. No. 3,152,454--Eberhart also teaches providing a temperature responsive valve means that is actuated when the temperature falls below a predetermined temperature for draining condensate from the sump.
U.S. Pat. No. 2,982,110--Kramer discloses an apparatus that selectively conducts condensate formed at the outdoor heat exchanger to the vicinity of the indoor heat exchanger during the heating cycle and in accordance with predetermined humidity condition in the vicinity of the latter heat exchanger, and treats the circulating air being heated by entraining the condensate therein.